2007 379 fan runs all the time

[mikkhh]

Well newer car AC pumps are constantly running, they have solenoid inside to regulate plate that is going to vary stroke of the pistons. There is no magnetic clutch anymore.

Bluetec Merc E class 350cdi around 2014 year was the car that had cooling fan running at 100%, there was fault code for low AC pressure. After fitting another pressure sensor fan runs like it should.

Without fan coming on and pump running the relief valve is going to go pop in matter of minutes. Has happened on similar Mercs to me.

After filling AC I check with gauges the pressures and when fan kicks on. On some older Sprinter vana it takes 25bar for fan to kick on.